In order to improve the performance of a golf club, golf club designers are often faced with the dilemma of trying to maximize the discretionary weight of a golf club, allowing that discretionary weight to be shifted and placed at more strategic locations within the golf club head.
In order to fully understand the challenges behind the very basic design guideline above, it is worth first investigating the meaning and importance of the concept of “discretionary weight”. Once the concept of discretionary weight has been explained, the discussion can then move towards how and where to strategically place the discretionary weight within a golf club head to improve the performance of a golf club.
Discretionary weight, as it is commonly known in the golf industry, refers to any additional weight that is not used up in the creation and formation of the basic elements of the golf club such as the face, the crown, the sole, the skirt, the hosel, and or any accompanying components. Because there are several components in a golf club, and each of those specific components has a minimum amount of weight required, there is a “theoretical minimum amount of weight” needed for the formation of a golf club. However, with the advances in material sciences and construction methodology, this “theoretical minimum amount of weight” can often be a floating number that decreases over time, resulting in an increase in the amount of discretionary weight that can be achieved in a golf club head.
Discretionary weight to a golf club designer is important because it allows the center of gravity of the golf club to be changed to achieve center of gravity goals to meet different design objectives. Because the laws of physics govern the impact between a golf club and a golf ball, the resultant trajectory of a golf ball is heavily influenced by the center of gravity of a golf club. Having a low and deep center of gravity will generally promote a golf club with high launching and low spinning golf ball, while having a high and forward center of gravity will promote a low launching and high spinning golf ball. Ultimately, determining the exact location of the center of gravity may be just as much of an art form as it is precise science, but having the maximum amount of discretionary weight allows the golf club designer the flexibility to achieve the maximum amount of center of gravity movements.
Hence, based on the above, it can be seen that one of the main concerns of a golf club designer is to maximize the amount of discretionary weight of a golf club by eliminating weight from locations of the golf club head that are now unnecessary due to certain material, design, or process improvements. By being conscious of the location where weight can be saved increases the discretionary weight, which can ultimately lead to improved golf club performance. U.S. Pat. No. 5,997,415 to Wood illustrates the concept of discretionary weight in a golf club head and one of the earlier attempts of increasing discretionary weight by using rings and frames.
U.S. Pat. No. 5,318,300 to Schmidt shows another one of the earlier attempts to manipulate the thickness of the striking face of a golf club head to improve performance. Although the intent of the Schmidt patent was to improve the ballspeed across the striking face, the thinning of specific portions of the striking face also saves weight and can help increase the discretionary weight.
U.S. Pat. No. 7,144,331 to Poynor shows another attempt to increase the discretionary weight of a golf club by having a wraparound face insert welded to the front face, resulting in an unsupported face area. This concept removes unnecessary material from certain portions of the golf club head to increase the discretionary weight within the golf club head.
Up till recently, most of the manipulation of wall thickness of a golf club head has always been focused on the thickest portion of the golf club head, the striking face. However, this portion of the club head, despite having the highest thickness, can only be thinned so much due to the fact that it must withstand the stresses of an impact with a golf ball. Hence, in order to find more discretionary weight, other portions of the golf club head must also be considered.
U.S. Pat. No. 7,789,773 to Rae et al. attempts to increase discretionary weight by adjusting the crown portion of a golf club head. U.S. Pat. No. 7,789,773 to Rae et al. attempts to do this by altering the geometry of the crown with recesses towards the ground plane to include a plurality of drop angles and recovery angles to create a crown portion that deviates from the conventional shape and geometry. This attempt, although could potentially be helpful in generating more discretionary weight, distorts the aesthetic appeal of a golf club head. Moreover, when the crown of a golf club head is manipulated, it often results in a destruction of the sound quality of golf club, further decreasing its desirability.
Hence, it can be seen that there exists a need for ways to further explore and increase the discretionary weight of a golf club head without disfiguring the aesthetic appeal of the golf club head itself. More specifically, there is a need in the field for ways to increase discretionary weight by focusing on the transition portion between the striking face and the aft portion of the golf club that leads to an increase in performance by normalizing the stresses at the crown portion of the golf club head and preserves the aesthetic appeal and audio feedback of a golf club head.